Accumulator.java

/*
 * Copyright 2010 Red Hat, Inc. and/or its affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.drools.core.spi;

import java.io.Serializable;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedExceptionAction;

import org.drools.core.WorkingMemory;
import org.drools.core.common.InternalFactHandle;
import org.drools.core.rule.Declaration;
import org.kie.internal.security.KiePolicyHelper;

/**
 * Accumulator
 *
 * Created: 04/06/2006
 *
 * @version $Id$
 */
public interface Accumulator
    extends
    Invoker {
    
    /**
     * Creates and return a context object for each working memory instance
     * 
     * @return
     */
    public Object createWorkingMemoryContext();
    
    /**
     * Creates the context object for an accumulator session.
     * The context is passed as a parameter to every subsequent accumulator
     * method call in the same session.
     * 
     * @return
     */
    public Serializable createContext();

    /**
     * Executes the initialization block of code
     * 
     * @param leftTuple tuple causing the rule fire
     * @param declarations previous declarations
     * @param workingMemory
     * @throws Exception
     */
    public void init(Object workingMemoryContext,
                     Object context,
                     Tuple leftTuple,
                     Declaration[] declarations,
                     WorkingMemory workingMemory) throws Exception;

    /**
     * Executes the accumulate (action) code for the given fact handle
     * 
     * @param leftTuple
     * @param handle
     * @param declarations
     * @param innerDeclarations
     * @param workingMemory
     * @throws Exception
     */
    public void accumulate(Object workingMemoryContext,
                           Object context,
                           Tuple leftTuple,
                           InternalFactHandle handle,
                           Declaration[] declarations,
                           Declaration[] innerDeclarations,
                           WorkingMemory workingMemory) throws Exception;
    
    /**
     * Returns true if this accumulator supports operation reversal
     * 
     * @return
     */
    public boolean supportsReverse();
    
    /**
     * Reverses the accumulate action for the given fact handle
     * 
     * @param context
     * @param leftTuple
     * @param handle
     * @param declarations
     * @param innerDeclarations
     * @param workingMemory
     * @throws Exception
     */
    public void reverse(Object workingMemoryContext,
                        Object context,
                        Tuple leftTuple,
                        InternalFactHandle handle,
                        Declaration[] declarations,
                        Declaration[] innerDeclarations,
                        WorkingMemory workingMemory) throws Exception;

    /**
     * Gets the result of the accummulation
     * 
     * @param leftTuple
     * @param declarations
     * @param workingMemory
     * @return
     * @throws Exception
     */
    public Object getResult(Object workingMemoryContext,
                            Object context, 
                            Tuple leftTuple,
                            Declaration[] declarations,
                            WorkingMemory workingMemory) throws Exception;
    
    
    /**
     * This class is used as a wrapper delegate when a security 
     * policy is in place.
     */
    public static class SafeAccumulator implements Accumulator, Serializable {
        private static final long serialVersionUID = -2845820209337318924L;
        private Accumulator delegate;

        public SafeAccumulator(Accumulator delegate) {
            super();
            this.delegate = delegate;
        }

        public Object createWorkingMemoryContext() {
            return AccessController.doPrivileged(new PrivilegedAction<Object>() {
                @Override
                public Object run() {
                    return delegate.createWorkingMemoryContext();
                }
            }, KiePolicyHelper.getAccessContext());
        }

        public Serializable createContext() {
            return AccessController.doPrivileged(new PrivilegedAction<Serializable>() {
                @Override
                public Serializable run() {
                    return delegate.createContext();
                }
            }, KiePolicyHelper.getAccessContext());
        }

        public void init(final Object workingMemoryContext, 
                final Object context, 
                final Tuple leftTuple, 
                final Declaration[] declarations, 
                final WorkingMemory workingMemory) throws Exception {
            AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
                @Override
                public Object run() throws Exception {
                    delegate.init(workingMemoryContext, context, leftTuple, declarations, workingMemory);
                    return null;
                }
            }, KiePolicyHelper.getAccessContext());
        }

        public void accumulate(final Object workingMemoryContext, 
                final Object context, 
                final Tuple leftTuple, 
                final InternalFactHandle handle, 
                final Declaration[] declarations, 
                final Declaration[] innerDeclarations, 
                final WorkingMemory workingMemory) throws Exception {
            AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
                @Override
                public Object run() throws Exception {
                    delegate.accumulate(workingMemoryContext, context, leftTuple, handle, declarations, innerDeclarations, workingMemory);
                    return null;
                }
            }, KiePolicyHelper.getAccessContext());
        }

        public boolean supportsReverse() {
            // we have to secure even this call because it might run untrusted code 
            return AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
                @Override
                public Boolean run() {
                    return delegate.supportsReverse();
                }
            }, KiePolicyHelper.getAccessContext());
        }

        public void reverse(final Object workingMemoryContext, 
                final Object context, 
                final Tuple leftTuple, 
                final InternalFactHandle handle, 
                final Declaration[] declarations, 
                final Declaration[] innerDeclarations, 
                final WorkingMemory workingMemory) throws Exception {
            AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
                @Override
                public Object run() throws Exception {
                    delegate.reverse(workingMemoryContext, context, leftTuple, handle, declarations, innerDeclarations, workingMemory);
                    return null;
                }
            }, KiePolicyHelper.getAccessContext());
        }

        public Object getResult(final Object workingMemoryContext, 
                final Object context, 
                final Tuple leftTuple, 
                final Declaration[] declarations, 
                final WorkingMemory workingMemory) throws Exception {
            return AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
                @Override
                public Object run() throws Exception {
                    return delegate.getResult(workingMemoryContext, context, leftTuple, declarations, workingMemory);
                }
            }, KiePolicyHelper.getAccessContext());
        }
        
        
    }

}